arXiv subjects

Matt C. J. Denton

Publications and source records attributed to Matt C. J. Denton.

2 recordsLinked to original sources

arXiv2025

Chirality-bolstered quantum Zeno effect enhances radical pair-based magnetoreception

Radical pairs in the flavoprotein cryptochrome are central to various magnetically sensitive biological processes, including the proposed mechanism of avian magnetoreception. Cryptochrome's molecular chirality has been hypothesized to enhance magnetic field effects via the chirality-induced spin selectivity (CISS) effect, yet the mechanism underlying this enhancement remains unresolved. In this work, we systematically investigate the impact of CISS on the directional magnetic sensitivity of prototypical radical pair reactions, analyzing two distinct models--one generating spin polarization and, for the first time, one generating coherence. We find that CISS-induced spin polarization significantly enhances magnetic sensitivity by introducing triplet character into the initial state and reinforcing the quantum Zeno effect, paralleling enhancements observed in triplet-born radical pairs subject to strongly asymmetric recombination. In contrast, CISS-generated spin coherence does not provide a significant improvement in sensitivity. These findings indicate that CISS is not itself a universal enhancer of sensitivity or coherence in radical-pair reactions, and its influence must be evaluated case by case, particularly in relation to the quantum Zeno effect. Additionally, we provide a unified interpolation scheme for modeling CISS-influenced initial states and recombination dynamics, encompassing the principal models currently discussed in the literature for singlet and triplet precursors.

quant-ph↗

arXiv2024

Quantum Control of Radical Pair Dynamics beyond Time-Local Optimization

We realize arbitrary waveform-based control of spin-selective recombination reactions of radical pairs in the low magnetic field regime. To this end, we extend the Gradient Ascent Pulse Engineering (GRAPE) paradigm to allow for optimizing reaction yields. This overcomes drawbacks of previously suggested time-local optimization approaches for the reaction control of radical pairs, which were limited to high biasing fields. We demonstrate how efficient time-global optimization of the recombination yields can be realized by gradient based methods augmented by time-blocking, sparse sampling of the yield, and evaluation of the central single time-step propagators and their Fréchet derivatives using iterated Trotter-Suzuki splittings. Results are shown for both a toy model, previously used to demonstrate coherent control of radical pair reactions in the simpler high-field scenario, and furthermore for a realistic exciplex-forming donor-acceptor system comprising 16 nuclear spins. This raises prospects for the spin-control of actual radical pair systems in ambient magnetic fields, by suppressing or boosting radical reaction yields using purpose-specific radio-frequency waveforms, paving the way for reaction-yield-dependent quantum magnetometry and potentially applications of quantum control to biochemical radical pair reactions. We demonstrate the latter aspect for two radical pairs implicated in quantum biology.

physics.chem-ph↗